I have many casual travel shots taken with a high resolution camera. I want to take the shots with high resolution because I'm not sure on beforehand if I want to print big or crop.

After reviewing the shots and having marked the ones I would like to keep in high resolution, I now want to downsample all the rest to 6MP in Lightroom because I have limited disk space for storing.

I know that Lightroom is not built for this and tried to prevent me from overwriting source, but I need to downsample and overwrite source because I have very limited disk space, and I'm shooting thousands of images a week at an extremely high resolution.

My current involves exporting to a different folder and then manually overwriting the source files. However, this has the negative side effect of getting conflicts with the meta data.

Irfanview will do this on a batch basis - it can be rapidly set to downsize according to a wide range of criteria and will delete the source files if desired. It's not something I've ever done as even if I was wanting to delete or overwrite the source file I'd tend to carry out the task and check the result first and then delete the files. Overwriting on the fly with no change of name etc risks confusion if the process aborts mid-task.
–
Russell McMahonOct 26 '12 at 16:05

4

Just out of curiosity, have you considered getting another hard drive? Disk space is SUPER CHEAP these days, and instead of permanently changing your RAW's or deleting photos, you could preserve them all with a 1Tb disk that would probably cost $60.
–
jrista♦Oct 26 '12 at 20:28

@jrista, I prefer to use SD cards because I can carry them on me at all time and they are easy to send home. I also keep a copy at places I stay. I quit my job and spend my time traveling (very lightweight) and shooting pictures from dusk to dawn.
–
grmOct 27 '12 at 15:58

@RussellMcMahon I think you are correct. Better use an external program and I also like irfanview. Thanks.
–
grmOct 27 '12 at 15:59

3 Answers
3

You can actually use Lightroom to do this - indirectly. But first with 1 Tb drives under $100 even already in cases would it not be better to just add storage?

But since you said that was not an option here is what you can do with Lightroom. Select the images you want in the Library view and use the Export... button to output .jpg files of the size you want. Then delete the selected full size files (using Lightroom). After that import the downsized files you exported in the first step.

Between deleting and re-importing you can also move the downsized files into the now empty directory that the full sized images were located. That depends on what kind of directory structure you want.

The best is to downsample the number of images you keep! Thousands of images per week must include very similar ones, missed shots, etc. Despite how good Lightroom is at indexing images, the more images you have the slower it gets.

As for your actual question. Plenty of programs can do this for you. My favorite is nconvert which can both downsample and compress quality. It is available for an incredible number of platforms! For a single image you can invoke it this way:

nconvert -q 90 -resize 50% 50% -overwrite DSCF0001.JPG

This will reduce the image quality to 90% and size by 50% in each direction. So a 24 MP becomes a 6 MP image. For a single directory you can replace the filename by a wildcard. For a whole directory tree, you need to run it in batch. A FOR (Windows/DOS) or foreach (Unix) loop can do this.

There is also xnview by the same author which runs nconvert in batch for you. Back in Lightroom you have to resynchronize your image folders once this is done.